The present invention relates to a pulley (belt pulley) and a CT (Computed Tomography) scanner using the pulley.
As a pulley of a large diameter such as a driven pulley used in a CT scanner there generally is used a cast aluminum pulley.
Such a cast pulley is manufactured by forming an annular member by casting and then forming teeth on a circumferential surface of the annular member with use of a machine tool such as, for example, a face lathe.
However, the above cast pulley involves the problem that machining such as lathing requires much time and labor.
There is another problem of an increase in cost because it is necessary to fabricate a mold for casting.
It is an object of the present invention to provide a pulley easy to manufacture and capable of being reduced its cost.
It is another object of the present invention to provide a CT scanner using a pulley which is easy to manufacture and whose cost can be reduced.
According to the present invention, for solving the foregoing problems, there is provided in the first aspect thereof a pulley comprising an annular portion formed by laminating generally annular plates, and a tooth portion formed along a circumferential surface of the annular portion, the tooth portion comprising a plurality of resin teeth having blades formed on the side opposite to the side which is opposed to the circumferential surface of the annular portion, the generally annular plates of the annular portion being each divided into a plurality of arcuate plates.
Since the pulley is constituted by an annular portion formed by laminating generally annular plates and a tooth portion comprising a plurality of resin teeth formed on a circumferential surface of the annular portion, the pulley can be manufactured easily at a reduced cost.
Moreover, the rigidity of the pulley can be enhanced easily by increasing the number of generally annular plates laminated.
The cost of the pulley can be further reduced because the generally annular plates are each constituted by arcuate plates which are easy for blanking.
A still further reduction of the cost can be attained because the tooth portion is constituted by a plurality of resin teeth.
In the second aspect of the present invention there is provided, in combination with the pulley in the first aspect, a pulley wherein the generally annular plate of each layer is divided in positions different from divided positions of the generally annular plate of a layer adjacent thereto.
Thus, the divided positions of the generally annular plates of the constituent layers are shifted from one another, whereby the deterioration of rigidity can be made smaller than the case where the divided positions are aligned.
In the third aspect of the present invention there is provided, in combination with the pulley in the first or the second aspect, a pulley wherein a component to be attached to a side face of the annular portion is mounted so as to straddle the arcuate plates adjacent to each other.
By mounting a component so as to straddle adjacent arcuate plates, the rigidity of the pulley is improved.
In the fourth aspect of the present invention there is provided a CT scanner comprising a rotatable frame mounted rotatably with respect to a fixed frame, a driven pulley mounted on the rotatable frame, a driving pulley mounted rotatably on the fixed frame and rotated by means of a drive source, and a belt wound between the driven pulley and the driving pulley, the driven pulley including an annular portion formed by laminating generally annular plates and a tooth portion formed along a circumferential surface of the annular portion, the tooth portion comprising a plurality of resin teeth having blades formed on the side opposite to the side which is opposed to the circumferential surface of the annular portion, the generally annular plates of the annular portion being each divided into a plurality of arcuate plates.
Since the driven pulley is constituted by an annular portion formed by laminating generally annular plates and a tooth portion comprising a plurality of resin teeth formed on a circumferential surface of the annular portion, the driven pulley can be manufactured easily at a reduced cost.
Moreover, by increasing the number of generally annular plates laminated, the rigidity of the pulley can be enhanced easily.
Further, since the generally annular plates are each constituted by arcuate plates which are easy for blanking, there can be attained a further reduction of cost.
It is possible to attain a still further reduction of cost because the tooth portion is constituted by a plurality of resin teeth.
As set forth above, according to the pulley in the first aspect of the present invention, there can be attained both easy manufacture and reduction of cost because the pulley is constituted by an annular portion formed by laminating generally annular plates and a tooth portion comprising a plurality of resin teeth formed on a circumferential surface of the annular portion.
Moreover, the rigidity can be enhanced easily by increasing the number of generally annular plates laminated.
A further reduction of cost can be attained since the generally annular plates are each constituted by arcuate plates which are easy for blanking.
Further, the formation of plural resin teeth to constitute the tooth portion can also contribute to the reduction of cost.
According to the pulley in the second aspect of the present invention, since the divided positions of the generally annular plates as constituent layers of the annular portion are shifted from one another, it is possible to keep low the deterioration of rigidity in comparison with the case where the divided positions are aligned.
According to the pulley in the third aspect of the present invention, the rigidity of the pulley is improved because a component is mounted so as to straddle arcuate plates adjacent to each other.
According to the CT scanner in the fourth aspect of the present invention, since the driven pulley used therein is constituted by an annular portion formed by laminating generally annular plates and a tooth portion comprising a plurality of resin teeth formed on a circumferential surface of the annular portion, the manufacture is easy and the cost can be reduced.
Besides, the rigidity can be enhanced easily by increasing the number of generally annular plates laminated.
A further reduction of cost can be attained because the generally annular plates are each constituted by arcuate plates which are easy for blanking.
Further, since the tooth portion is constituted by a plurality of resin teeth, the reduction of cost can also be attained.
Further objects and advantages of the present invention will become apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.